1. Field of the Invention
The present invention relates to a process for forming an image using an electrophotographic process or an electrostatic recording process, in which an electrostatic latent image is developed and transferred to an intermediate transfer member, and an image is transferred and fixed to a recording medium by heating or the like procedure.
2. Description of Related Art
Various systems have been known as an electrophotographic process, such as a system disclosed in Japanese Patent Publication No. 23910/1967. In the electrophotographic process, a fixed image is formed in such a manner containing plural steps in that a latent image is electrically formed on a photoreceptor using a photoconductive substance by various methods, the latent image is developed by using a toner, the toner image on the photoreceptor is transferred to a transfer material, such as paper, through or not through an intermediate transfer member, and then the transferred image is fixed by application of heat, pressure, or heat and pressure, or by using a solvent vapor. The toner remaining on the photoreceptor is cleaned by various methods depending on necessity, and the plural steps are repeated.
Because the electrophotographic system using no organic solvent unlike ordinary printing, it is not restricted in setting environment, and because it is a simple system requiring no expert skill unlike ordinary printing, it is widely spread to office and home. Due to popularization and progress of computers and networks thereof caused with wide spread of sophisticated information-intensive society in recent years, there are increasing needs of on-demand printing of digital information, and further improvement in image quality of the electrophotographic system is demanded.
Among various types of the electrophotographic systems, those using a transferring and fixing process disclosed in Japanese Patent Publication No. 41679/1971. Japanese Patent Publication No. 63757/1991 and Japanese Patent Laid-Open No. 107950/1993 cause no disorder of a toner image upon transferring and thus are effective for improvement of image quality since the transferring step and the fixing step are simultaneously carried out.
However, because a toner image is newly formed on the intermediate transfer member after completion of the transferring and fixing step, followed by repeating the transferring and fixing step, toner-filming, such as a non-transferred toner after the transferring and fixing step, minute offset and paper powder, remains on the surface of the intermediate transfer member, which brings about such drawbacks that it adversely affects formation of the next toner image, it is offset on the next transfer material, and the releasing property of the intermediate transfer member is deteriorated to be liable to cause releasing failure of the transfer material.
In the systems where the transferring step and the fixing step are independently carried out, those disclosed in Japanese Patent Laid-Open No. 167902/1994 and Japanese Patent Laid-Open No. 250557/1994 are effective to maintain the surface of a fixing device clean owing to the functions including cleaning of the surface of the fixing device and application of a releasing oil. However, in the transferring and fixing process, the surface is necessarily maintained to a further clean state in comparison to the system where the transferring step and the fixing step are independently carried out since the transferring step is again conducted after the fixing step. Therefore, in the case where the system disclosed in Japanese Patent Laid-Open No. 167902/1994 is applied to the transfer fixing process, it is insufficient since such problems occur that toner-filming through the cleaning member occurs on the intermediate transfer member, and the releasing oil damages the transferred image.
Silicone rubber, fluorine rubber and a fluorine resin have been generally used as a material for the surface of the fixing device. As a method for preventing wear-out and deterioration of releasing property of the material of the surface of the fixing device, improving the cleaning property and improving the reliability, a method of application of a releasing oil is effective in any case, and the method has been used in the system where the transferring step and the fixing step are independently carried out.
Since silicone rubber originally contains a free silicone oil, toner components are liable to be deposited in the rubber when the heat fixing and printing are repeated without supply of a silicone oil, and the deposition can be prevented by supplying and coating the silicone oil.
Fluorine rubber has such an advantage, in comparison to the silicone rubber, that the wear resistance is high, but sufficient releasing property cannot be obtained unless a releasing film is formed by adsorbing or reacting a modified silicone on the fluorine rubber surface as disclosed in Japanese Patent Laid-Open No. 230784/1992.
In the case of the fluorine resin also, the reliability, such as prevention of sticking of the toner due to the presence of pinholes and prevention of wear-out of paper edges, can be remarkably improved by supplying silicone oil.
The method for coating the releasing material includes a donor roll system, a web system, a system using a roll wound with nonwoven cloth and a system using a roll having an oil added inside the roll, as disclosed in Japanese Patent Laid-Open No. 289746/1994 and Japanese Patent Laid-Open No. 75495/1994.
However, when these systems are applied to the transfer fixing process, the oil cannot be uniformly coated on the fixing surface unless the oil supplying amount is 1 xcexcl or more per A-4 size paper. When the supplying amount is decreased, unevenness in oil supply, which is referred to as so-called oil stripes, is liable to occur, whereby the releasing material is attached to the intermediate transfer member to contaminate the image forming member such as a photoreceptor, or nonuniformity in cleaning occurs.
As described in the foregoing, it is difficult to improve the reliability of fixing in color duplicators and color printers using the transfer fixing process through the conventional technique having been disclosed, and at present, a process for forming an image using a newly designed transfer fixing process is being demanded.
The invention is developed to solve the problems associated with the conventional art and to provide a process for forming an image using a transfer fixing process that can maintain high image quality for a long period of time.
As a result of earnest investigations of adhesion property of the cleaning material made by the inventors with respect to the cleaning property of an intermediate transfer member for the transfer fixing process, it has been found that when a cleaning material having the specific viscoelastic characteristics is supplied to and removed from the intermediate transfer member, toner-filming on the intermediate transfer member is removed to maintain the surface of the intermediate transfer member clean, whereby high image quality of the transferred toner image and high quality of the fixed toner image can be maintained for a long period of time. Thus, the invention has been completed.
According to an aspect of the invention, the process for forming an image contains the steps of: forming a toner image on an image bearing member by developer; transferring a toner image formed on the image bearing member to an intermediate transfer member; simultaneously transferring and fixing the toner image on the intermediate transfer member to a recording medium; releasing the recording medium having the toner image fixed thereon from the intermediate transfer member; and cleaning a toner remaining on the intermediate transfer member using a cleaning material. The cleaning material contains thermoplastic resin particles having a volume average particle diameter of about from 1 to 50 xcexcm and a storage modulus (Gxe2x80x2) of about from 1xc3x97103 to 1xc3x97105 Pa at a temperature Tmc, at which the cleaning material has a loss modulus (Gxe2x80x3) of 1xc3x97104 Pa.
According to another aspect of the invention, the apparatus for forming an image contains: a developing unit for forming a toner image on an image bearing member by developer; a transferring unit for transferring a toner image formed on the image bearing member onto an intermediate transfer member; a simultaneous transferring and fixing unit for simultaneously transferring and fixing the toner image on the intermediate transfer member onto a recording medium; a unit for releasing the recording medium having the toner image fixed thereon from the intermediate transfer member; and a unit for cleaning a toner remaining on the intermediate transfer member using a cleaning material. The cleaning material contains thermoplastic resin particles having a volume average particle diameter of about from 1 to 50 xcexcm and a storage modulus (Gxe2x80x2) of about from 1xc3x97103 to 1xc3x97105 Pa at a temperature Tmc, at which the cleaning material has a loss modulus (Gxe2x80x3) of 1xc3x97104 Pa.